From Traderpedia

Definition: A value measure of the flow of domestic goods and services produced by an economy over a period of time, such as a year.

Only output values of goods for final consumption and investment are included because the values of primary and intermediate production are assumed to be included in final prices. GDP is sometimes aggregated and shown at market prices, meaning that indirect taxes and subsidies are included; when these have been eliminated, the result is GDP at factor cost. The word gross indicates that deductions for depreciation of physical assets have not been made. See also Gross National Product.